The present invention relates to cabinet assemblies for housing electronic apparatus or the like and, more particularly, to such cabinet assemblies and methods for forming the assemblies which are characterized by high integrity radio frequency interference seals and improved structural strength.
Electronic equipment of various sorts is frequently assembled in a modular form wherein a typically box-like cabinet assembly is constructed for receiving one or more individual electronic sub-assemblies. The cabinet assemblies may, in turn, be housed within a larger chassis or may be utilized in a stand-along mode. In either case, the electronic sub-assemblies are often contained on printed circuit boards which include suitable mounting apparatus enabling the boards to be easily inserted or removed from the cabinet assemblies as the need arises. This modular arrangement facilitates logistical operations associated with maintaining the equipment in that, for example, repair operations, including stock piling of spare parts, may be performed on a sub-assembly basis by relatively inexperienced maintenance personnel in a minimum period of time. These latter considerations largely account for the recent popularity of such modularized electronic equipment.
Due to the nature of electronic equipment, and especially particular apparatus such as radio receivers and transmitters, the cabinet assemblies preferably supply an operational environment secure from radio frequency interference (RFI). If allowed to exceed certain levels, radio frequency interference permeating the cabinet assembly from an external source can seriously degrade the performance of the electronic sub-assemblies by subjecting them to excessive levels of noise. On the other hand, radiation of radio frequency interference from within the cabinet assembly can adversely affect the performance of other nearby equipment. To avoid these problems, most military agencies, for example, provide strict specifications defining precise limits of radio frequency interference to which various types of equipment may be subjected as well as to maximum permissible levels of radiation.
One technique commonly used to decrease the radio frequency interference susceptibility of cabinet assemblies adapted for housing electronic apparatus is to secure the various joints of the cabinets with special radio frequency interference shielding materials. These shielding materials, an exemplary form of which may comprise a strip of silicone rubber impregnated with wire fibers or the like, are normally glued to one or more surfaces of the cabinet assembly to seal the joints for preventing externally generated radio frequency interference from exposing and interfering with the electronic equipment contained within the cabinet and for preventing internally generated radio frequency interference from radiating outwardly from the cabinet. While such prior art efforts have been successful to a degree, they have not always reduced radio frequency interference leakage to an acceptable level in a manner which is conveniently and cost effectively implemented.
In addition to providing adequate radio frequency interference shielding, the cabinet assembly is also preferably relatively light-weight and inexpensively manufacturable while, at the same time, possessing adequate structural strength. These requirement have heretofore been considered to be somewhat conflicting and have not been fully satisfied by any known prior art cabinet assembly useful for housing electronic apparatus.